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Lesson 3: Parallel and perpendicular

Parallel and perpendicular lines review

Review the basics of parallel and perpendicular lines.  Identify and draw parallel and perpendicular lines in some practice problems.

What are $\text{perpendicular lines}$‍  and $\text{parallel lines}$‍ ?

$\text{Perpendicular lines}$ are lines that meet at right angles.
$\text{Parallel lines}$ are always the same distance apart from each other — no matter how far they are extended, they will never meet.

Practice set 1: Identify parallel and perpendicular lines

Problem 1A
Which of the following pairs of sides in $\mathrm{△}GAZ$ are perpendicular?

Want to try more problems like this? Check out this exercise.

Practice set 2: Draw parallel and perpendicular lines

Problem 2A
Any pair of points can be connected by a line.
Use the green line to connect the pair of black points that makes a line parallel to the blue line segment.

Want to try more problems like this? Check out this exercise.

Want to join the conversation?

• Quick question how do you prove that lines are parallel? I can't seem to find that on here and i really need to know!
• If you draw a line through the 2 lines, it should be perpendicular to both lines.
• I am having trouble remember these. Anyone have any tips to help me remember?

Edit : Case Closed. But thank you Taylyn for answering my question! Everyone have a nice day.
• Yes. In the word Parallel, the double L's are side by side, and if going on in a straight line, would never touch. So, the double L's in Parallel are, well, parallel. Use those as an example to help you remember what parallel means.
• Does a perpendicular line ALWAYS have to be 90 degrees? Just a Question
• Yes, a perpendicular line must always be at a 90-degree angle
• Are perpendicular any kind of lines that intersect each other? I've got to know this!
• Yes, perpendicular lines intersect each other with 4 90-degree angles.
• Why does the human brain have to know what geometry is?
• So it can identify shapes and measure things. It also helps make the human brain grow.

Hope this helps :D
• What happens if a Parallel line goes through a regular line so that make it perpendicular so what is that.
• If the parallel line goes through the line, the lines will not be parallel anymore, so they will only be perpendicular if they meet at a right angle.
• does perpendicular line have to be the exactly 90 degrees?
• It always have to be exactly at a right angle, and a right angle is always 90 degrees so yes.